Using a mobile phone for 10 years or more increases the risk of ear tumours by four times, research suggests.
A 750-people study by Sweden's Karolinska Institute found the risk of acoustic neuroma rose by 3.9 times on the side of the head the phone is used.
There was no increase in risk on the other side of the head - giving an overall rise in risk of 1.9 times.
Acoustic neuroma is a benign tumour in the auditory nerve, which can cause brain and nerve damage.
It affects one in 100,000 people.
Those who had used mobile phones for less than 10 years were not at a greater risk, the team reported.
Out of the 750 people who took part in the study, 150 had acoustic neuroma and of those one in 11 had used a mobile phone for at least a decade.
Professor Anders Ahlbom, from the Stockholm-based institute, told BBC News Online http://www.emfnews.org/store/http://www.emfnews.org/products.html